Geology & Geochemistry of Combustible Minerals No. 1 (178) 2019, 47-62.
Yuri KHOKHA, Oleksandr LYUBCHAK, Myroslava YAKOVENKOInstitute of Geology and Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine, Lviv,
The analysis of literature was carried out and the main criteria for determining the gas generating potential of rocks were determined. These criteria are divided into two groups: the first one is geochemical, which includes the content of organic carbon and the thermal maturity of the rocks. The second group combines the geological and economic criteria that determine the suitability of rocks for the removal of hydrocarbon gases from them. In our opinion, the most important group of criteria should be considered a geochemical group.
Traditionally, to determine the ability of organic matter to form hydrocarbons, the Rock-Eval analysis was used. As a result, determined are the total organic carbon (TOC) and other parameters, such as hydrogen index (HI) or production index (PI).
In this paper, we are trying to expand the range of parameters that can be used to determine the gas generation potential of the rocks. The elemental composition of the organic matter dissipated in the rocks, in general terms, should affect on the composition and amount of hydrocarbons that they synthesize. To determine the influence of elemental composition on the gas-generating potential, equilibrium thermodynamics is used in conjunction with the Jaynes’ formalism.
Samples for investigation – bituminous argillites from Menilite suite of Oligocene, were taken from two fields of the Ukrainian Carpathians. For samples, the elemental composition of the organic matter and the mineral composition of the inorganic part (by X-ray crystallography) are determined. The data on the elemental composition came into the calculation, the result of which is the distribution of the additive components in the organic matter and the composition of gases.
The results of the calculations were compared with the results obtained by the Rock-Eval method. It was found that the calculation by the thermodynamic method gives understated results. On the other hand, it allows the establishment of a change in the chemical structure of organic matter of rocks. We are outlined ways to further improvement of the method.
gas-generating potential, Jaynes’ formalism, equilibrium thermodynamic, dissipated organic matter.
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